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LinuxWatch writes "'It's been long promised, but there it is now,' began Linux creator Linus Torvalds, announcing the 2.6.25 Linux kernel. He continued, 'special thanks to Ingo who found and fixed a nasty-looking regression that turned out to not be a regression at all, but an old bug that just had not been triggering as reliably before. That said, that was just the last particular regression fix I was holding things up for, and it's not like there weren't a lot of other fixes too, they just didn't end up being the final things that triggered my particular worries.' There were numerous changes in this revision of the OS. The origins of some of those fixes is detailed in Heise's brief history of this kernel update."

Also kernelnewbies.org seems to be very slow at the moment. Here is a copy of the important changes section from their 2.6.25 changelog page:

1.1. Memory Resource Controller

Recommended LWN article (somewhat outdated, but still interesting): "Controlling memory use in containers"

The memory resource controller is a cgroups-based feature. Cgroups, aka "Control Groups", is a feature that was merged in 2.6.24, and its purpose is to be a generic framework where several "resource controllers" can plug in and manage different resources of the system such as process scheduling or memory allocation. It also offers a unified user interface, based on a virtual filesystem where administrators can assign arbitrary resource constraints to a group of chosen tasks. For example, in 2.6.24 they merged two resource controllers: Cpusets and Group Scheduling. The first allows to bind CPU and Memory nodes to the arbitrarily chosen group of tasks, aka cgroup, and the second allows to bind a CPU bandwidth policy to the cgroup.

The memory resource controller isolates the memory behavior of a group of tasks -cgroup- from the rest of the system. It can be used to:

* Isolate an application or a group of applications. Memory hungry applications can be isolated and limited to a smaller amount of memory.
* Create a cgroup with limited amount of memory, this can be used as a good alternative to booting with mem=XXXX.
* Virtualization solutions can control the amount of memory they want to assign to a virtual machine instance.
* A CD/DVD burner could control the amount of memory used by the rest of the system to ensure that burning does not fail due to lack of available memory.

The configuration interface, like all the cgroups, is done by mounting the cgroup filesystem with the "-o memory" option, creating a randomly-named directory (the cgroup), adding tasks to the cgroup by catting its PID to the 'task' file inside the cgroup directory, and writing values to the following files: 'memory.limit_in_bytes', 'memory.usage_in_bytes' (memory statistic for the cgroup), 'memory.stats' (more statistics: RSS, caches, inactive/active pages), 'memory.failcnt' (number of times that the cgroup exceeded the limit), and 'mem_control_type'. OOM conditions are also handled in a per-cgroup manner: when the tasks in the cgroup surpass the limits, OOM will be called to kill a task between all the tasks involved in that specific cgroup.

Code: (commit 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)

1.2. Real Time Group scheduling

Group scheduling is a feature introduced in 2.6.24. It allows to assign different process scheduling priorities other than nice levels. For example, given two users on a system, you may want to to assign 50% of CPU time to each one, regardless of how many processes is running each one (traditionally, if one user is running f.e. 10 cpu-bound processes and the other user only 1, this last user would get starved its CPU time), this is the "group tasks by user id" configuration option of Group Scheduling does. You may also want to create arbitrary groups of tasks and give them CPU time privileges, this is what the "group tasks by Control Groups" option does, basing its configuration interface in cgroups (feature introduced in 2.6.24 and described in the "Memory resource controller" section).

Those are the two working modes of Control Groups. Aditionally there're several types of tasks. What 2.6.25 adds to Group Scheduling is the ability to also handle real time (aka SCHED_RT) processes. This makes much easier to handle RT tasks and give them scheduling guarantees.

Documentation: sched-rt-group.txt

Code: (commit 1, 2, 3, 4)

There's serious interest in running RT tasks on enterprise-class hardware, so a large number of enhancements t

i'm not 100% sure on what you're asking, but I'm guessing you are trying to change from smbfs to cifs, which isn't a big deal. Go in to the kernel config and select "CIFS", deselect "SMBFS" (you can have both selected, but there is no need), recompile, reboot. more details: http://www.gentoo-wiki.com/HOWTO_Setup_Samba [gentoo-wiki.com]

Shared memory sounds good. IRIX uses it with Xsgi as an alternative transport for local connections, and it significantly speeds up clients that use lots of small requests, like motif applications with thousands of widgets and x-resources.